It is known that oil-filled transformers are used in extra-high voltage levels of by way of example 380 kV/110 kV. A transformer of this type can include by way of example a power rating of greater than 100 MVA and a weight in the region of by way of example 100 t and higher. Oil-filled transformers are characterized by virtue of the fact that the actual transformer is arranged in an oil tank that is filled with oil. The oil acts both as a cooling medium and also as an electrical insulating medium. The electrical connections of the actual transformer are guided through the oil-filled intermediate space between the tank and the transformer to the corresponding end line connections or rather connection sites. Care is to be taken that the lines are embodied and arranged in such a manner that sufficient electrical breakdown strength is provided. In principle, a greater gap between the transformer and the tank wall improves the breakdown strength but on the other hand the installation size of the transformer is increased in an extremely disadvantageous manner.
So-called battery systems have been provided on the high voltage side and the so-called battery systems encompass the respective end line tubes in a similar manner to that of a cylinder and thus improve the field distribution within the oil tank. Insulated lines or stranded conductors have been used for controlling the voltage of transformers, the control process mostly being performed on the high voltage-side, and the insulated lines or stranded conductors are guided for example in bundles between the tapping sites of a respective winding and an associated stepping switch. Stranded conductors of this type have been arranged in a self-supporting manner on so-called switching frames. Switching frames can include a multiplicity of vertical and horizontal strips in which the stranded conductors are clamped in a costly and laborious manner using rollers and small pressboard plates and they acquire their electrical strength exclusively from the insulation on the stranded conductors. As a result, large oil-filled gaps are used with respect to objects that have other potentials such as for example windings and this can increase the installation size of the oil tank.
Furthermore, switching frames are characterized by a very limited mechanical strength and are therefore susceptible to short-circuit forces. It is therefore known to mount vertical strips at intervals of less than 700 mm in order to be able to absorb any short-circuit forces that occur. The high number of strips that is used as a result prevents the distances to the windings from being increased and consequently promotes tracking path flashovers along the strips. Switching frames of this type involve a very labour intensive assembly process as a result of their type of construction and the high number of fastening parts.